Toothbrush

ABSTRACT

A toothbrush ( 1 ), comprising a tufted portion in which a plurality of tufts ( 4 ) to ( 7 ) formed of bristles made of synthetic resin are fixed to a head portion ( 3 ) of a toothbrush body made of synthetic resin, some of the plurality of tufts ( 4 ) to ( 7 ) having substantially the same horizontal cross sectional shape, and being arranged adjacent to each other in a central axis direction of the toothbrush in such a manner that a distance between centers of the tufts becomes substantially equal to a length in a width direction of a tooth.

TECHNICAL FIELD

The present invention relates to a toothbrush excellent in a plaque removal efficacy or cleaning properties, and more particularly to a toothbrush excellent in effect of removing dental plaque (plaque) deposited between teeth (interproximal part), particularly on an interproximal-papilla part, gingival margin, periodontal pocket, etc.

BACKGROUND ART

Various toothbrushes in which the tip shape of each bristle formed of a filament made of synthetic resin has been devised are conventionally known as a toothbrush which has been improved in a plaque removal efficacy and cleaning properties in a narrow part, such as an interproximal part and a periodontal pocket. For example, various toothbrushes in which the bristle tip is tapered so as to improve the insertion properties to a narrow part such as an interproximal part or a periodontal pocket have been proposed. For example, the following toothbrushes are mentioned: a toothbrush whose synthetic monofilament tufted in a bristle filling hole of a toothbrush has a tapered shape in which the diameter of the bristle in each part located at a given length from the top end of a tapered portion is in a given ratio to the diameter of the bristle on a base (Patent Document 1.); a toothbrush in which both ends of a filament, which has been tufted in a bristle filling hole of a brush tip while being bent in a U shape, have different shapes in which one end of the filament is formed into a globular shape and the other end is tapered or a toothbrush in which the filament is tufted while one end of the filament being protruded relative to the other end (Patent Document 2.); and a toothbrush in which long tapered bristles and short tapered bristles are tufted by tuft in a head portion in such a manner that the long tapered bristles and the short tapered bristles mutually co-exist (Patent Document 3). Furthermore, various toothbrushes in which the end of a filament has been branched have been proposed, such as a toothbrush in which sea-island composite fibers are configured so that only the island part is exposed at the bristle tip to form the core bristles having a given length by immersing the end of a filament made of a composite synthetic resin having a cross sectional shape in which island parts made of polyamide resin are scattered in a sea part made of polyester resin in an acid or alkaline solution for dissolution of the sea part, and then the composite fibers are tufted in a head portion (Patent Document 4.); a toothbrush in which the bristle tip has been branched into a plurality of numbers and each branched bristle is acutely tapered and which is obtained by immersing a bristle whose base cross sectional shape in a head portion is a shape in which a plurality of unit cross sectional components of a given shape, such as a circular shape, elliptical shape, triangular shape, or hexagonal shape are connected in an acid or alkali chemical solution (Patent Document 5); a toothbrush in which a plurality of acutely tapered branched bristles are formed at the end and bristles, some of which are different in length from a specific branched bristle, are tufted (Patent Document 6.).

Moreover, various toothbrushes in which the horizontal cross sectional shape of a tuft fixed to a head portion of a toothbrush has been devised have also been proposed. For example, the following toothbrushes are known: a toothbrush in which bristles are tufted in a bristle filling hole having a substantially triangular shape (e.g., Patent Document 7), a toothbrush in which the tip surface of a tuft having an angular cross sectional shape, such as a triangular shape or a fan shape, is cut to form an inclined flat surface (e.g., Patent Document 8.), a toothbrush in which a tuft whose horizontal cross sectional shape has an acute angle part, such as a crescent shape or a triangular shape, is arranged in the peripheral part of a bristle filling surface of a head portion in such a manner that the acute-angle part faces outward (e.g., Patent Document 9); and a toothbrush in which a tuft whose horizontal cross sectional shape is tapered in the longitudinal axis direction from the outer peripheral part of the bristle side or in a direction facing the outer periphery of a bristle side is arranged (e.g., Patent Document 10).

Patent Document 1: Japanese Unexamined Patent Application Publication No. 6-141923 Patent Document 2: Japanese Unexamined Patent Application Publication No. 7-284412 Patent Document 3: Japanese Unexamined Patent Application Publication No. 11-75939 Patent Document 4: Japanese Unexamined Patent Application Publication No. 9-322821 Patent Document 5: Japanese Unexamined Patent Application Publication No. 2003-144229 Patent Document 6: Japanese Unexamined Patent Application Publication No. 2003-199626 Patent Document 7: Japanese Unexamined Utility Model Application Publication No. 56-58227

Patent Document 8: U.S. Pat. No. 1,981,657 specification

Patent Document 9: Japanese Unexamined Patent Application Publication No. 2004-41403 Patent Document 10: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2002-502268 DISCLOSURE OF THE INVENTION Technical Problems to be Solved

As described above, various toothbrushes are conventionally known in which the tip shape of a bristle and the cross sectional shape of a tuft have been devised for the purpose of improving effects of removing and cleaning dental plaque deposited on an interproximal part or the periodontal pocket. However, with respect to a toothbrush in which the bristle tip is tapered (tapered shape), the insertion properties of the bristle to a narrow part, such as the interproximal part and the periodontal pocket, are improved, but, in some cases, the rigidity of the bristle decreases, and thus the plaque removal efficacy and cleaning properties over an entire tooth including a relatively flat part, such as a tooth surface, are insufficient. Moreover, in terms of a cross sectional shape of a tuft, a toothbrush has not yet been obtained in which the dental plaque removal and cleaning properties at each part, such as the interproximal part, especially the interproximal-papilla part and the periodontal pocket in a gingival margin and a cervical margin are simultaneously achieved. Thus, an object of the present invention is to provide a toothbrush excellent in the plaque removal efficacy and cleaning properties in the interproximal part, a part between the teeth and the gums, etc. Further, an object of the present invention is to provide a toothbrush which is excellent in the operativity in the mouth, design properties, etc.

Means to Solve the Problems

The toothbrush of the present invention has a tufted portion in which a plurality of tufts formed of bristles made of synthetic resin are fixed to a head portion of a toothbrush body made of synthetic resin, in which some of the plurality of tufts have substantially the same horizontal cross sectional shape, and are arranged adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance between the centers of the tufts becomes substantially equal to the length in the width direction of a tooth.

It is preferable that the distance between the centers of the tufts having the same cross sectional shape and arranged adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance between the centers of the tufts becomes equal to the length in the width direction of a tooth be 5 to 12 mm. Moreover, it is preferable that the tufts having the same cross sectional shape and arranged adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance becomes equal to the length in the width direction of a tooth be arranged at the side edge of the head portion.

It is preferable that the horizontal cross sectional shape of the tufts having the same cross sectional shape and arranged adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance between the centers of the tufts becomes equal to the length in a width direction of a tooth be a substantially triangular cross sectional shape and that the tuft having a substantially triangular cross sectional shape be fixed to a head portion while a tapered part of a substantially triangular cross sectional shape directing in the same direction. Moreover, it is preferable that the tuft having a substantially triangular cross sectional shape have a substantially triangular cross sectional shape which is tapered from the outer edge of the head portion toward the central axis of the toothbrush. It is preferable that the tuft having a triangular cross sectional shape have a horizontal cross sectional shape which is inscribed in a circle having a diameter of 1.4 to 4.5 mm.

Moreover, in a toothbrush according to a preferable embodiment, tufts having an elongated cross sectional shape extending in the central axis direction of the toothbrush are arranged between the plurality of tufts having a triangular cross sectional shape and arranged in the central axis direction of the toothbrush. In this case, it is more preferable that the tuft having an elongated cross sectional shape be arranged outward in the width direction of the head portion relative to the tuft having a triangular cross sectional shape. Moreover, it is preferable that the horizontal cross sectional shape of the tuft having an elongated cross sectional shape be substantially quadrilateral.

It is preferable that the bristles forming the tufts having the same cross sectional shape and arranged adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance between the centers of the tufts becomes substantially equal to the length in a width direction of a tooth be tapered. The bristle whose tip is tapered may be branched at the tip thereof. Moreover, it is preferable that the tuft formed of bristles whose tips are rounded in a usual manner be fixed to a position closer to the central axis of the toothbrush relative to a position of the tufts formed of the bristle having a tapered tip.

In the toothbrush of the present invention, a brush tip surface formed of tip surfaces of tufts may have unevenness. Moreover, the central portion of the tip surface of each tuft formed of the tips of the bristles may be formed into a convex shape.

In the toothbrush of the present invention, the length of the bristle having a tapered tip may be equal to or longer than the length of the bristle whose tip is rounded in a usual manner.

In the toothbrush of the present invention, the tuft may be thermally bonded to a head portion. In this case, it is preferable that the number of the bristles of the tuft having a triangular cross sectional shape and/or the number of the bristles of the tuft having an elongated cross sectional shape be substantially an integral multiple of the number of bristles which are picked out by a device for picking out bristles in the same amount when the tuft is thermally bonded to the head portion. Or, it is preferable that the horizontal cross sectional area of the bristles of the tuft having a triangular cross sectional shape and/or the horizontal cross sectional area of the bristles of the tuft having an elongated cross sectional shape be substantially an integral multiple of the horizontal cross sectional area of bristles in an opening, from which bristles are picked out by a device for picking out bristles in the same amount when the tuft is thermally bonded to the head portion.

EFFECT OF THE INVENTION

In the toothbrush of the present invention, since tufts having substantially the same horizontal cross sectional shape are arranged at given intervals and adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance between the centers of the tufts becomes substantially equal to the length in the width direction of a tooth, the tufts are well-fitted to the interproximal part, particularly a position corresponding to an interproximal-papilla part, and is excellent in the cleaning properties and the plaque removal efficacy in the parts. Moreover, when the tufts adjacent to each other at given intervals are fixed to the side edge of the head portion, fitting of the toothbrush to the interproximal part is further facilitated by a scrub method in which tooth brushing is effected by bringing the bristle tip of the toothbrush into contact with the teeth in a perpendicular manner, and then minutely moving the toothbrush forward and backward (in the central axis direction of the toothbrush) or the Bass method in which tooth brushing is effected by bringing the bristle tip of the toothbrush into contact with the boundary between the teeth and the gingival slantingly, and then minutely moving the toothbrush forward and backward. Furthermore, the tufts adjacent to each other at given intervals have a substantially triangular horizontal cross sectional shape and are fixed while a tapered part of a substantially triangular shape directing in the same direction, and when the horizontal cross sectional shape of the tuft having a triangular cross sectional shape has a substantially triangular shape which is tapered from the outer edge of the head portion toward the central axis of the toothbrush, the toothbrush becomes excellent in fitting properties to the interproximal-papilla part.

In the case of a toothbrush in which tufts having an elongated cross sectional shape extending in the central axis direction of the toothbrush are arranged between tufts having a triangular cross sectional shape and adjacent to each other in the central axis direction of the toothbrush, when tooth brushing is performed by the scrub method or the Bass method, the tuft having an elongated cross section is located in a gingival margin between the teeth and the gingiva in a tooth neck and the periodontal pocket part thereof and simultaneously the tuft having a triangular cross sectional section at both teeth at both sides is located in the interproximal part between both teeth. Thus, both of the gingival margin and periodontal pocket, and interproximal part can be cleaned at a time, and therefore the cleaning properties or the plaque removal efficacy are excellent. Furthermore, when the tuft having an elongated cross sectional shape is arranged outward of the head portion relative to the tuft having a triangular cross sectional shape, the tuft having an elongated cross sectional shape and the tuft having a triangular cross sectional shape can be surely brought into contact with the gingival margin, the periodontal pocket, and the interproximal-papilla parts at both sides thereof, which further facilitates cleaning of the parts and removal of dental plaque of the parts.

In the case where the horizontal cross sectional shape of the tuft having an elongated cross section is substantially quadrilateral, when tooth brushing is performed by moving a toothbrush forward and backward (central axis direction) by the scrub method or the Bass method, cleaning and dental plaque clearance of the periodontal pocket are facilitated.

Moreover, when the bristle of the tuft having a triangular cross section is tapered, and preferably the tuft having an elongated cross section is also tapered, the bristle tip enters the periodontal pocket and a narrow space of the interproximal part, whereby the cleaning properties and plaque removal efficacy are excellent. Furthermore, when the bristle having a tapered tip is branched at the tip, the insertion properties to the periodontal pocket or the interproximal part are excellent and the cleaning properties and plaque removal efficacy are high. In contrast, when the bristle of the tuft fixed to the side closer to the central axis of a toothbrush in a head portion is a bristle whose tip is rounded in a usual manner, the rigidity of the bristle is high, a dirt removing effect in the tooth surface is high, and cleaning properties over a whole tooth are improved.

When the length of the bristle having a tapered tip is equal to or longer than the bristle whose tip is rounded in a usual manner, the bristle having a tapered tip is easily inserted in the periodontal pocket or the interproximal part with little resistance of the bristle having a rounded tip, and the cleaning properties and plaque removal efficacy in the parts are also increased.

Moreover, it is preferable that the brush tip surface formed of tuft tip surfaces be not flat but uneven because the bristle tips are easily fitted to irregularities of a dentition. Furthermore, it is preferable that the center of the tuft tip surface formed of the bristle tips in each tuft fixed to a head portion be formed into a convex shape because the insertion properties of the tuft to a concave portion are improved.

In the case of a toothbrush in which bristles are thermally bonded to a head portion without using a anchor wire, the thickness of the head portion can be reduced; the operativity of the toothbrush in the mouth is excellent; and the tuft is easily fixed to a head portion while forming a triangular cross sectional shape. In general, when tufts are thermally bonded to a head portion, a tuft in which bristles which have been cut into a given length beforehand are bundled is placed in a die member (first die) by a device for picking out bristles (e.g., picker, but not limited to a picker); a space (cavity) for molding a brush is formed between the die member (first die) and a brush molding die (second die); and then injecting and charging a molding material of a brush body in the molding space for molding. In the case of the toothbrush of the present invention, when the number or the horizontal cross sectional area of the bristles of the tuft having a triangular cross sectional shape and/or the number or the horizontal cross sectional area of the bristles of the tuft having an elongated cross sectional shape are substantially an integral multiple of the number of the bristles which are picked out by a device, such as a picker, for picking out the bristles in the same amount or substantially an integral multiple of the horizontal cross sectional area of the bristles in an opening through which to pick up the brushing bristles, the dimension of the tuft can be changed only by adjustment of the number of times of picking out by the picker or the like, which is very convenient in a production process.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating a head portion of a toothbrush according to one embodiment of the present invention.

FIG. 2( a) is a front view of the toothbrush and FIG. 2( b) is a plan view thereof.

FIG. 3( a) is an enlarged front view of the head portion, FIG. 3( b) is an enlarged plan view thereof, and FIG. 3( c) is an enlarged side view thereof.

FIG. 4( a) is a plan view of a head portion of a toothbrush according to another embodiment and FIG. 4( b) is a plan view of a head portion of a toothbrush according to still another embodiment.

FIG. 5 is a view schematically showing that a tuft of a toothbrush is brought into contact with an interproximal part and a gingival margin.

FIG. 6( a) is an enlarged view of the tip of a branched bristle, and FIGS. 6( b) to (h) are cross sectional views of a filament of a branched bristle.

FIG. 7( a) is a front view of a bristle having a plurality of core bristles protruded at the tip, FIG. 7( b) is a perspective view thereof, and FIGS. 7( c) to (e) are cross sectional views of a filament having a sea-island structure.

FIG. 8( a) is a perspective view of a bristle having a plurality of core bristles protruded at the tip according to another embodiment, and FIG. 8( b) is a cross sectional view of a filament of the bristle.

FIG. 9( a) is a perspective view of a bristle having a single core bristle protruded at the tip, and FIG. 9( b) is a cross sectional view thereof.

FIG. 10( a) is a perspective view of a bristle having a single core bristle protruded at the tip according to another embodiment, and FIG. 10( b) is a cross sectional view thereof.

FIG. 11( a) is a perspective view of a bristle having a single core bristle protruded at the tip according to another embodiment, and FIG. 11( b) is a cross sectional view thereof.

FIG. 12( a) is a perspective view of a bristle having a single core bristle protruded at the tip according to another embodiment, and FIG. 12( b) is a cross sectional view thereof.

FIGS. 13( a) to (c) are cross sectional views of a filament having a cross-sectional sheath-core structure.

BRIEF DESCRIPTION OF NUMERALS

-   1. Toothbrush -   2. Neck -   3. Head portion -   3 a. Bristle filling surface -   4. Tuft -   4 a. Brush tip surface -   5. Tuft -   5 a. Brush tip surface -   6. Tuft -   6 a. Brush tip surface -   7. Tuft -   7 a. Brush tip surface -   8. Tuft -   9. Bristle filling part -   10. Brush body -   11. Handle -   21. Branched bristle -   22. Unit cross-section component -   23. Sheath part -   24. Core bristle -   25. Sea part (sheath part) -   26. Island part (core part) -   27. Tapered part -   28. Protrusion -   29. Concave groove -   A. Adhesive layer -   B. Interproximal part -   d. Distance between centers of tufts -   F. Filament -   N. Interproximal papilla part -   S. Gingival margin -   t. Thickness of head portion -   w. Length in a width direction of a tooth -   X. Central axis of a toothbrush

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 to 3 show a toothbrush according to one embodiment of the present invention. FIG. 1 is a perspective view illustrating a head portion. FIG. 2( a) is a front view of the toothbrush and FIG. 2( b) is a plan view thereof. FIG. 3( a) is a front view of a head portion, FIG. 3( b) is a plan view thereof, and FIG. 3( c) is a side view thereof. In a toothbrush 1, a large number of tufts 4, 5, 6, and 7 formed of bristles are fixed to a head portion 3 at one end of a brush body 10 to form a bristle filling part 9.

The brush body 10 is integrally molded by injection molding of a thermoplastic resin, and has a head portion 3 which is tufted with tufts 4 to 7, a handle 11 for holding the toothbrush 1, and a thin and long neck 2 for connecting the head portion 3 and the handle. There is no limitation on the type of thermoplastic resin as a raw material of the brush body 10. A resin can be mentioned which contains, as a main component, a resin selected from polyester resin, such as polybutylene terephthalate resin, polypropylene terephthalate resin, polyethylene terephthalate resin, polyethylenenaphthalate resin, PCTA resin, and PCTG resin; and polyolefin resin, such as polyacetal resin (homopolymer, copolymer), polycarbonate resin, aliphatic polyamide resin, aromatic polyamide resin, polypropylene, and polyethylene. Preferably, a resin is used which contains, as a main component, a resin selected from polyester resin, such as polybutylene terephthalate resin, polyethylene terephthalate resin, PCTA resin, and PCTG resin, and polyacetal resin. The PCTA resin is a copolymer of an ester compound of cyclohexane dimethanol (CHDM) and terephthalic acid (TPA) and an ester compound of CHDM and isophthalic acid (IPA). The PCTG is a copolymer of an ester compound of an ethylene glycol and CHDM and an ester compound of CHDM and TPA, and both the PCTA resin and PCTG are saturated polyester resins. The main component as used herein refers to the above-mentioned resin which is contained in a proportion of 50% by weight or more in a substance which is blended or mixed as an alloy with another resin for use, or the above-mentioned resin whose repeat unit of a polymer is contained in a proportion of 50% by weight or more in a copolymer with another resin. Mentioned as another thermoplastic resin which can be used when mixed or copolymerized with a thermoplastic resin serving as the above-mentioned main component are ABS resin, polystyrene resin, EPDM, acrylic resin, polyurethane resin, polyarylate, thermoplastic elastomer, silicone resin, fluororesin, etc., besides the above-mentioned resins which can be used as a main component.

A so-called anchorless wire toothbrush is preferable in which the tufts 4 to 7 are fixed to the head portion 3 of the toothbrush 1 by bundling bristles made of synthetic resin to form tufts, and thermally bonding the tufts, to the head portion 3, without using a anchor wire by heat sealing, fuse-in method, or in-mold method. As a method of fixing the tufts to the head portion 3 without using a anchor wire, a conventionally known method is acceptable. Mentioned as the fuse-in method is a method described in, for example, Japanese Unexamined Patent Application Publication No. 60-241404, Japanese Unexamined Patent Application Publication No. 61-76104, or Japanese Unexamined Patent Application Publication No. 2-99002 and mentioned as the in-mold method are methods described in, for example, Japanese Unexamined Patent Application Publication No. 61-268208, Japanese Unexamined Patent Application Publication No. (Translation of PCT Application) No. 2-503150, Japanese Unexamined Patent Application Publication No. 9-182632, Japanese Unexamined Patent Application Publication No. (Translation of PCT Application) No. 9-512724, and Japanese Unexamined Patent Application Publication No. 2003-102552. By thermally bonding the tufts 4 to 7 to the head portion 3 without using a anchor wire by the above-mentioned methods, the burial depth of the tuft into the head portion 3 can be reduced, and the thickness t of the head portion 3 can be considerably reduced to, for example, 4 mm or lower, and further 3.5 mm or lower. Thus, a toothbrush can be produced which is excellent in the operativity in the mouth and is preferable in terms of design properties.

As shown in FIG. 1 to FIG. 3, on the bristle filling surface 3 a of the head portion 3, a large number of the tufts 4 to 7 are arranged in a plurality of rows extending in the central axis direction X of the toothbrush 1. In the central tuft row, one large tuft 4 located at the forefront of the head portion 3 and four tufts 5 smaller than the above-mentioned large tuft 4 (five tufts in total) are arranged along the central axis X. Each of the tufts 4 and 5 has a horizontal cross sectional shape formed into a substantially quadrilateral shape extending in the central axis direction X. At both the right and left side edges of the central tuft row, relative to the first, third, and fifth tufts 4, 5, and 5 from the end of the central tuft row, three tufts 5 having the same dimension and the same cross sectional shape as those of the four tufts 5 in the central row are arranged at given intervals at positions adjacent to each other in the direction orthogonal to the central axis X. These tufts 4 and 5 are formed of bristles whose tips are rounded in a usual manner, and the brush tip surface s 4 a and 5 a formed of bristles of the tufts 4 and 5 are formed into a chevron shape having two inclined surfaces which are inclined to the front and the back from the each center of the bundle in the central axis direction X of the toothbrush 1.

Moreover, between three tufts 5 of the tuft rows at the right and left sides, two tufts 6 having a substantially triangular cross sectional shape are fixed whose horizontal cross sectional shape is tapered from the outer edge of the head portion 3 toward the central axis X of the toothbrush, i.e., from the outer edge of the head portion 3 to the inside. Furthermore, at the side edge located substantially at the center of the toothbrush 1 in the central axis direction X in the head portion 3, a tuft 7 having a quadrilateral horizontal cross sectional shape extending in the central axis direction X is fixed while the tuft 7 being sandwiched between the tufts 6,6 having a triangular cross section. The tuft 6 having a triangular cross sectional shape and the tuft 7 having a quadrilateral cross sectional shape fixed to the side edge therebetween (black-colored tuft in FIG. 3) are formed of bristles each having a tapered tip, unlike other tufts 4 and 5 (white-colored tuft in FIG. 3), and the brush tip surfaces 6 a and 7 a formed of bristle tips are formed at a flat surface parallel to the bristle filling surface 3 a.

The tufts 6 having a triangular cross section are arranged in such a manner that the distance (“d” shown in FIG. 3( b)) between the centers of two tufts 6 adjacent to each other in the central axis direction of the toothbrush 1 is nearly equal to the length (“W” shown in FIG. 5) in the width direction of a tooth. The distance between the centers of the tufts 6 having a triangular cross section varies according to specifications of a toothbrush. For example, the distance is different between a toothbrush for adults and a toothbrush for children, and is, for example, 5 to 12 mm. In the case of a usual toothbrush, the distance d is about 6 to 10 mm, and preferably 7 to 9.5 mm. There is no limitation on a cross sectional shape of the tuft 6 having a triangular cross section. The cross sectional shape thereof is preferably a regular triangle or an isosceles triangle because such a shape is easily fitted to any interproximal-papilla parts, such as an anterior tooth and a molar. Furthermore, as the dimension of the tuft 6 having a triangular cross section, it is preferable for the tuft 6 to have a cross sectional shape which is inscribed in a circle having a diameter of 1.4 to 4.5 mm, and preferably 2.0 to 4.0 mm. When the tufts 6 having the above-mentioned center-to-center distance d and having a triangular cross section having the above-mentioned dimension are arranged adjacent to each other in the central axis direction X of a toothbrush, the triangular cross-section tufts 6 are well fitted to the interproximal part, especially the interproximal-papilla part.

Next, FIG. 4( a) is a plan view showing a toothbrush according to another embodiment of the present invention. According to a toothbrush 1A of this embodiment, a bristle filling part 9 has a structure such that two tufts 7 formed of bristles having a tapered tip and having a rectangular horizontal cross sectional shape extending in the central axis direction X are fixed between the three tufts 6, formed of bristles having a tapered tip, and fixed to the side edge of the head portion 3 in such a manner as to have a triangular horizontal cross sectional shape which is tapered from the outer edge of the head portion 3 toward the central axis X of a toothbrush, i.e., from the outer edge of the head portion 3 toward the inside.

FIG. 4( b) is a plan view showing a toothbrush according to still another embodiment of the present invention. In a toothbrush 1B of this embodiment, a bristle filling part 9 has a structure such that three tufts 6 formed of bristles having a tapered tip and having a triangular cross sectional shape which is tapered from a side edge of the head portion 3 toward the central axis X of the toothbrush are arranged in the central axis direction X of the toothbrush at the side edge of the bristle filling part 3 and three tufts 8 formed of bristles whose tip is rounded in a usual manner, and having a substantially triangular cross sectional shape which is tapered from the central axis X of the toothbrush toward a side edge of the head portion 3 are fixed in two rows.

Also in the toothbrushes 1A and 1B of embodiments shown in FIGS. 4( a) and 4(b), it is preferable that the tufts 6 having a triangular cross section be arranged in such a manner that the distance d between the centers of two tufts 6 adjacent to each other in the central axis direction of the toothbrush 1 is nearly equal to the length (“W” shown in FIG. 5) in the width direction of a tooth. For example, the distance is about 5 to 12 mm. In the case of a usual toothbrush, the distance is about 6 to 10 mm, and preferably about 7 to 9.5 mm. Furthermore, it is preferable that a cross sectional shape has a dimension in such a manner as to be inscribed in a circle having a diameter of 1.4 to 4.5 mm, and preferably 2.0 to 4.0 mm.

In the toothbrushes 1, 1A, and 1B of the above-mentioned embodiments of the invention, the tufts 6 having bristles having a tapered tip are fixed to the head portion 3 in such a manner as to have a substantially triangular cross sectional shape, and a plurality of tufts having a triangular cross section adjacent to each other in the central axis direction X of a toothbrush are arranged in such a manner that the distance d between the centers of the respective tufts 6 is nearly equal to the length W in the width direction of a tooth. Thus, such toothbrushes are excellent in cleaning properties and a plaque removal efficacy in the interproximal part, especially the interproximal-papilla part. Moreover, since the tufts 6 having a triangular cross section are fixed to the side edge of the head portion, the tuft 6 having a triangular cross section is well fitted to the interproximal part, especially the interproximal-papilla part when tooth brushing is performed by a scrub method in which tooth brushing is effected by bringing the bristle tip of the toothbrush into contact with the teeth in a perpendicular manner, and then minutely moving the toothbrush forward and backward or the Bass method in which tooth brushing is effected by bringing the bristle tip of the toothbrush into contact with the boundary between the teeth and the gingival slantingly, and then minutely moving the toothbrush forward and backward. Thus, cleaning properties and dental plaque clearance in the above-mentioned parts are excellent. Furthermore, in the toothbrushes 1 and 1A of the above-mentioned embodiments, since the tuft 7 having an elongated horizontal cross section extending in the central axis direction of the toothbrush is arranged between the tufts 6 having a triangular cross section, the tuft 7 having an elongated cross section is located in the gingival margin S at the boundary of a tooth T and the gum G and simultaneously the tuft 6 having a triangular cross section is well fitted to the interproximal part B between teeth T at both sides, especially the interproximal-papilla part N as illustrated in FIG. 5. Thus, the gingival margin S and the interproximal part B (interproximal-papilla part N) can be cleaned at a time. Furthermore, since the tuft 6 having a triangular cross section and the tuft 7 having an elongated cross section are tapered, the bristle tip enters a periodontal pocket and a narrow space of the interproximal part B. Thus, the above-mentioned parts are cleaned and dental plaque deposited on the parts is removed. Furthermore, since the tuft 7 having an elongated cross section is arranged at the outer edge of the head portion relative to the tuft 6 having a triangular cross section, the tuft 7 having an elongated cross section and the tuft 6 having a triangular cross section can be surely brought into contact with the gingival margin S and the interproximal-papilla part N at both sides, which further facilitates cleaning of the parts and removal of dental plaque of the parts.

Usable as a material of bristle used in the present invention are synthetic resin known as a bristle of a toothbrush, such as polyamide resin, such as nylon and aramid; polyester resin, such as polybutylene terephthalate (PBT), polypropylene terephthalate (polytrimethylene terphthalate, PPT, or PTT) or polyethylene terephthalate (PET); and polyolefin resin, such as polypropylene (PP) and polyethylene (PE). Moreover, there is no limitation on the tip shape of a tapered bristle, and known tapered bristles can be used. The shape and length of the tapered part are not limited. In view of the rigidity, cleaning properties, etc., of a bristle, the length of the tapered part is preferably half or lower of the bristle length (length from the bristle filling surface 3 a to the tip of bristle). Moreover, as the tapered bristle, various kinds of tapered bristle can be used besides bristle which are tapered in a usual manner.

For example, FIG. 6( a) shows the end of a filament F made of synthetic resin of a bristle used for the toothbrush of the present invention according to one embodiment. The filament F is branched in a plural numbers at the bristle tip, and the branched bristle tip (branch bristle 21) is a tapered bristle which has been tapered beforehand. The filament F having the branch bristle 21 at the tip has a cross sectional shape in which a plurality of unit cross-section components 22 having various shapes, such as a circle, ellipse, triangle, and hexagon, are connected as illustrated in, for example, FIGS. 6( b) to (h). Moreover, the filament F having the branch bristle 21 at the tip may have a multi-leaf shaped cross section in which a single or a plurality of leaves which is/are different in the cross sectional area from a specific leaf is connected to the surrounding of the specific leaf via a joint part which is thinner than the minimum dimension of the cross section of a leaf having the minimum cross sectional area. In this case, the number of leaves is practically 2 to 5. However, the number of leaves is not limited, and is determined according to the purpose of use. By immersing the filament F made of synthetic resin having the above-mentioned cross sectional shape in a chemical solution, such as caustic soda (NaoH), acid, and an organic solvent, and picking up the resultant, two or more tapered branch bristles 21 are formed at the tip as shown in FIG. 6( a). At this time, the shape and length of the branch bristle 21 can be suitably adjusted according to the concentration of a chemical solution, immersion period of time, filament picking-up rate from the chemical solution, etc. As a material of the filament F made of synthetic resin, any of the above-mentioned various known synthetic resins can be used.

With respect to the filament F made of synthetic resin having the tapered branch bristle 21, the length from the branch point to the end is half or lower, and preferably ⅓ or lower of the height of the bristle (i.e., bristle length) in a tufted state. Moreover, the cross sectional area of a part closer to the base end relative to the branch point (bristle base), i.e., a part which is not subjected to dissolution treatment, varies according to the cross sectional shape and the like. It is optimum that the cross sectional area is 0.001 to 0.5 mm², and is usually 0.01 to 0.2 mm², and preferably 0.01 to 0.1 mm². When the cross sectional area of the bristle base is lower than 0.001 mm², the bristle elasticity is low and the rigidity required for brushing is insufficient. When the cross sectional area of the bristle base exceeds 0.5 mm², the bristle is thick and the insertion properties to a narrow part are poor. Therefore, the cross sectional area of the bristle base is suitably determined in view of relevant factors, such as a cross sectional shape and a material on the basis of the lower limit and the upper limit. Moreover, in the case of a bristle having two kinds of branch bristles whose lengths are different from each other, it is preferable that the length of a short branch bristle is in the range of 1/10 to 9/10 of the length of a long branch bristle. When the length of the short branch bristle is shorter than 1/10 of the length of a long branch bristle, a brushing effect to be obtained by the short branch bristle is poor. When the length of the short branch bristle is longer than 9/10 thereof, an effect to be obtained by varying the lengths of the branch bristles cannot be sufficiently demonstrated.

FIGS. 7( a) and 7(b) show a filament F made of synthetic resin having a tapered tip, similarly as described above, according to another embodiment. In the filament F made of synthetic resin, a plurality of core bristles 24 (e.g., three core bristles 24 in FIG. 7) are protruded from the end of a sheath part 23. The filament F whose end is brunched by protruding the plurality of core bristles 24 from the end of the sheath part 23 refers to a composite synthetic resin monofilament F (hereinafter referred to as a composite monofilament) in which, for example, an island part is formed of a material containing polyamide resin, such as nylon and aramid, as a main component and a sea part is formed of a material containing polyester resin, such as polybutylene terephthalate, as a main component. For example, by immersing the composite filament F having a sea-island structure, as shown in FIGS. 7( c) to 7(e), in which the above-mentioned polyester resin is used for a sea part 25 and a nylon resin is used for an island part 26 in caustic soda (NaOH), and picking up the resultant, the sea part 25 is melt-removed from the end to thereby expose the island part 26. Thus, as shown in FIGS. 7( a) and 7(b), a bristle is produced in which a plurality of core bristles 24 are protruded from the end of the sheath part 23 forming the outer surface of a bristle. In this case, the tapered shape of the sheath part 23 end and the exposure length of the core bristle 24 can be suitably adjusted according to the concentration of caustic soda, immersion period of time, filament picking-up rate from caustic soda, etc. Furthermore, as shown in FIG. 8( b), by immersing a filament F made of synthetic resin having a cross sectional shape in which a plurality of unit cross-section components 22 are connected and each unit cross-section component 22 has a sheath-core structure or a sea-island structure in a chemical solution, such as caustic soda (NaOH), acid, and an organic solvent, and picking up the resultant, a filament F (bristle) in which the core bristles 24 are protruded from each tip of a plurality of tapered branch bristles 21 as illustrated in FIG. 8( a) can be obtained.

As the size of the filament F serving as the bristle in which a plurality of core bristles 24 are protruded from the end of the sheath part 23, it is preferable that the diameter of the base (sheath-core composite part) be 0.150 to 0.300 mm, that the diameter of the core bristle 24 be 0.03 to 0.07 mm, that the exposure length of the core bristle be 0.2 to 4.0 mm, and it is more preferable that the exposure length of the core bristle be 0.5 to 4.0 mm. Moreover, it is preferable that the length from the bristle filling base to the bristle tip (length of a bristle exposed from the bristle filling surface 3 a, i.e., bristle length) be 7 to 11 mm. Furthermore, when the diameter of the base end is defined as 100%, it is preferable that the end of the composite part be tapered in such a manner that the diameter is 70±15% at a position away from a base point at the boundary between the exposed core bristle 24 and the composite part toward the composite part side by 1 mm, 89±8% at a position away from the base point by 3 mm, and 93±17% at a position away from the base point by 5 mm. When the diameter of the composite part is adjusted to 0.150 to 0.300 mm, the diameter of the core bristle 24 is adjusted to 0.03 to 0.07 mm, and the exposure length of the core bristle 24 is 0.2 to 4.0 mm, the insertion properties to a narrow part in the mouth, reachability to the deep part of the narrow part in the mouth, and a dental plaque removal action of the core bristle 24 which has reached the deep part are improved. When the exposure length of the core bristle 24 is adjusted to 0.5 to 4.0 mm, the insertion properties to a narrow part in the mouth, reachability to the deep part of the narrow part in the mouth, and the dental plaque removal action of the core bristle 24 which has reached there are further improved. When the length from the bristle filling base of the tufted sea-island composite fiber to the bristle tip is in the range of 7 to 11 mm, sufficient bristle elasticity required for obtaining a cleaning effect can be achieved and the insertion properties to narrow parts, such as the interproximal part, are excellent, resulting in ease of operation.

FIG. 9( a) shows a filament F made of synthetic resin according to still another embodiment of a tapered bristle used in the present invention. This filament F made of synthetic resin has a cross sectional shape of a sheath-core structure or a sea-island structure. It is preferable that the sheath part or the sea part formed of a material containing polyester resin as a main component be tapered toward the bristle tip and that a single core bristle 24 formed of a material preferably containing polyamide resin as a main component be exposed at the bristle tip. More specifically, as shown in FIG. 9( b), the core part 26 at the end of the composite monofilament F having a sheath-core structure in which the sheath part (sea part) 25 is arranged surrounding one core part (island part) 26 is exposed, and the core bristle 24 is protruded at the end as shown in FIG. 9( a). In the case of the composite monofilament F of the above-mentioned sheath-core structure, among cross sectional areas, i.e., cross sectional areas of a whole composite monofilament F containing the core part 26 and the sheath part 25, it is preferable that the cross sectional area of the core part 26 be 15 to 80%, and more preferably 40 to 80%. Thus, while maintaining an appropriate bristle elasticity at the bristle base end, due to the core bristle 24 which has a cross sectional area exposed at the end of 15 to 80%, cleaning properties in a narrow part can be demonstrated without damaging the gingiva and the bristle tip is prevented from bending and from becoming uneven when thermally bonded to the head portion 3.

A method of exposing the core part is the same as in the case of exposing a plurality of core parts shown in FIGS. 7 and 8. When a single core part 26 is exposed, a method of removing the sheath part 25 by a mechanical method, besides a chemical method, can be employed. In the case of a chemical removal method, for example, by immersing the end of a composite monofilament F in which a polyamide resin is used for the core part 26 and a polyester resin, such as PBT, is used for the sheath part 25 in a alkaline chemical solution, such as caustic soda (NaOH), to thereby expose the core part 26. Thus, a filament F (bristle) in which the core bristle 24 is protruded at the end can be formed.

A tapered part 27 continuous to the core bristle 24 is inevitably formed at the end of the sheath part 23 (sea part 25) dissolved as described above. The tapered angle or the like can be easily adjusted by controlling the immersion period of time and the like. Due to the formation of the tapered part 27, the insertion properties and reachability to a narrow part in the mouth are further improved.

The cross sectional shape of each of the composite monofilament F and the core part 26 shown in FIG. 9( b) is substantially in the form of a circle. The outside diameter b2 of the composite monofilament F is adjusted to 0.16 mm to 0.25 mm and the outside diameter b1 of the core part 26 is adjusted to 40 to 90%, and more preferably 60 to 80% of the outside diameter of the composite monofilament F. It is preferable that the bristle length from the bristle filling base of the tufted bristle to the bristle tip be in the range of 6 to 12 mm. When the bristle length is extremely long, the operativity in the mouth is bad, and, furthermore, the bristle is too soft to obtain a sufficient cleaning effect. In contrast, when the bristle length is extremely short, flexibility of bristles under brushing is insufficient, which deteriorates the sense of use and insertion properties to the interproximal part. The exposure length of the core bristle 24 is adjusted to 5 to 50%, more preferably 10 to 50% of the bristle length and, specifically, is adjusted to a suitable range of 0.5 to 4.0 mm. When the exposure length of the core bristle 24 is lower than 5%, reachability to the interproximal part, periodontal pocket of the cervix part, and a deep part of the pit and fissure or the like is not sufficient. When the core bristle 24 in which the core part 26 is exposed is longer, a cleaning effect to a narrow and deep part is higher, but, in contrast, durability decreases. The length of the core bristle 24 capable of maintaining practical durability is 50% or lower of the bristle length, and specifically, about 4.0 mm or lower.

The tip shape of the exposed core bristle 24 is arbitrary, and can be processed into a suitable shape, such as a hemisphere shape. In this embodiment, a material of the core part 26 is polyamide resin, and the core bristle 24 exposed from the sheath part 23 is extended straightly in a cylindrical manner. Thus, the bristle tip is prevented from bending or the like when thermally bonded to the head portion 12.

Next, FIG. 10 shows an example where the cross sectional shapes of the core part 26 and the core bristle 24 in which the core part 26 is exposed from the sheath part 25 are formed into substantially polygon shapes. FIG. 11 shows an example where a plurality of protrusions 28 extending in the axial direction are formed on the outer peripheral surface of the core part 26. FIG. 12 shows an example where a plurality of concave grooves 29 extending in the axial direction are formed on the outer peripheral surface of each of the core part 26 and the core bristle 24.

When the cross sectional shape of the core part 26 is formed into a substantially polygonal shape having an acute angle part similarly as in the filament F shown in FIG. 10, the sheath part end remains in such a manner as to be engaged in a recess formed in the core part 26 to form an engaging part in the core part exposed base end. This makes it possible to prevent the sheath part from separating from the core part exposed base end during use and can improve durability. Also in the case of the filament F shown in each of FIG. 11 and FIG. 12, similarly as in the case where the cross sectional shape of the core part 26 is formed into a substantially polygonal shape as described above, an engaging part in which the protrusion 28 or the concave groove 29 is engaged in the end of the sheath part 23 is formed to thereby prevent the end of the sheath part 25 from separating.

FIGS. 13( a) and 13(b) show composite monofilaments F in which the core part 26 and the sheath part 25 are bonded to each other via an adhesive layer A. Thus, the above-mentioned separation of the sheath part end can be further surely prevented. Furthermore, FIG. 13( c) shows that the cross sectional shape of the composite monofilament F is formed into a substantially the same as the cross sectional shape of the core part 26. Thus, the thickness of the sheath part 25 is substantially uniform in the circumferential direction and the sheath part 25 is difficult to separate from the core part 26.

In the toothbrush of the present invention, when bristles are thermally bonded to a head portion by in-mold method, fuse-in method, etc., without using a anchor wire, a tuft tip surface and a brush tip surface formed of the tuft tip surface are made uniform to have a desired shape. Thus, the brush tip surface formed of the bristle tip can be formed into an arbitrary shape by bringing the bristle tip into contact with a back plate. For example, a tuft tip surface is formed into a chevron shape in which the central part is high (long bristle length) and the length decreases (short bristle length) toward the periphery as in the tufts 4 and 5. Furthermore, the brush tip surface can be formed into a three-dimensional shape in which unevenness is formed in the width direction (direction orthogonal to the central axis X of a toothbrush) of a bristle filling part. As described above, when the tuft tip surface is formed into a chevron shape (convex) or unevenness is formed on the brush tip surface, a toothbrush can be obtained in which the insertion properties of the tuft to the narrow part such as the interproximal part, between the teeth and the gum are further improved, and cleaning properties and a plaque removal efficacy are further excellent.

Moreover, a toothbrush can be formed by picking out a tuft, in which bristles which have been cut into a given length beforehand are bundled, by a device for picking out bristles, thermally integrating the bristles into a tuft, and then injecting a molding material of a main body. It is preferable that the number of the tufts 6 having a triangular cross section and/or the tufts 7 having an elongated cross section of the present invention be substantially integral multiple of the number of bristles picked out by the device for picking out the bristles. The substantially integral multiple as used herein means that an error of ±10% is included based on the numerical value which becomes an integral multiple. This is because the number of the bristles picked out varies depending on the mechanism of the device for picking out bristles. Moreover, the horizontal cross sectional area of the tuft 6 having a triangular cross section and/or a tuft 7 having an elongated cross section may be substantially integral multiple of a horizontal cross sectional area of the bristle in an opening of a picking out device for picking out the bristles of a picking out device. Furthermore, in view of the efficiency at the time of production, it is more preferable that the number or the cross sectional area of the tuft 6 having a triangular cross section and/or the tuft 7 having an elongated cross section be substantially the same as the number of bristles picked out by the device for picking out bristles or the horizontal cross sectional area of bristles in an opening of device for picking out bristles. Thus, according to the toothbrush of the present invention, the filament made of synthetic resin which has been tapered beforehand or has been subjected to usual tip-rounding processing is thermally bonded to the head portion 3 of the toothbrush body 10 by an inserting method, fuse-in method, etc., thereby forming the horizontal cross sectional shape of each tuft into a suitable shape.

Or, a method may be acceptable which involves once placing a tuft, obtained by thermally bundling brushing bristles, to a plate in such a manner that the final bristle filling pattern is reflected to thereby form a pattern of a bristle filling part, and molding a brush body in such a manner as to include the plate to which the tuft is placed to thereby form a bristle filling part. More specifically, a tuft having an arbitrary horizontal cross sectional shape can be fixed to the head portion 3 by forming the shape of a tuft containing hole of a tuft holding metal fitting (first die) at the time of bonding bristles (tuft) to the head portion 3 or a bristle filling hole formed on the head portion 3 into a triangular shape, rectangular shape, and other arbitrary shapes.

In the above-described embodiments, only a manually-operated toothbrush 1 which has a handle 11 is described. However, the toothbrush of the present invention can be formed into a brush for electric toothbrushes having a driving unit by shortening the handle.

Example 1

A handle 10 of a toothbrush shown in FIG. 2 was molded using polybutylene terephthalate (PBT) by injection molding. The toothbrush with a bristle filling part 9 was produced, by an in-mold method, in which, among tufts of a bristle filling part 9 shown in FIG. 1 and FIG. 3, tufts 7 at both side of a head portion 3 are omitted and bristles obtained by rounding the ends of nylon filaments (hereinafter referred to as “usual bristle”) were tufted as tufts 6,6 having a triangular cross section in such a manner that the cross sectional shape was inscribed in a circle 2.7 mm in diameter and the center-to-center distance was adjusted to 7.0 mm. The specifications of the tuft are shown in Table 1.

TABLE 1 Specification of tuft of Toothbrush Thickness of Number of Length of Material bristle bristles per bristle of mil bristle filling (H) Bristle bristle (μm) hole mm shape Tuft 4 Nylon 7 156/hole  8 Rounded (177.8) Tuft 5 Nylon 7 78/hole 8 Rounded (177.8) Tuft 6 Nylon 7 78/hole 8 Rounded (177.8)

Example 2

A toothbrush was produced following the procedure of Example 1 except changing the center-to-center distance between the tufts 6, 6 having a triangular cross section to 9.4 mm in the toothbrush of Example 1.

Example 3

A toothbrush was produced following the procedure of Example 1 except that the tufts 6, 6 having a triangular cross section were tufted in such a manner as to form a triangular cross section which was tapered from the central axis of a toothbrush to the side edge of a head portion in the toothbrush of Example 1.

Example 4

A toothbrush was produced following the procedure of Example 1 except filing tufts (usual bristle) having a quadrilateral cross section in place of the tufts 6,6 having a triangular cross section in the toothbrush of Example 1.

Example 5

A toothbrush was produced following the procedure of Example 1 except filing tufts (usual bristle) having a circular cross section in place of the tufts 6,6 having a triangular cross section in the toothbrush of Example 1.

Example 6

A toothbrush was produced following the procedure of Example 1 except that the tufts 6,6 having a triangular cross section are formed into a shape which was inscribed in a circle 2.0 mm in diameter in the toothbrush of Example 1.

Example 7

A toothbrush was produced following the procedure of Example 1 except that the tufts 6,6 having a triangular cross section are formed into a shape which was inscribed in a circle 4.0 mm in diameter in the toothbrush of Example 1.

Example 8

A toothbrush was produced following the procedure of Example 1 except filling a tuft 7 (usual bristle with a bristle length of 8 mm) having a quadrilateral cross section shown in FIG. 3( b) between the tufts 6,6 having a triangular cross section in the toothbrush of Example 1.

Example 9

A toothbrush was produced following the procedure of Example 8 except forming the tufts 6,6 having a triangular cross section and the tuft 7 having a quadrilateral cross section from bristles in which PBT was used for a sea part (sheath part), nylon was used for an island part (core part), the bristle tip had three branches, and the bristle length was 10 mm (hereinafter referred to as a “special bristle”) in the toothbrush of Example 8.

Example 10

A toothbrush was produced following the procedure of Example 1 except that the tufts 6,6 having a triangular cross section are formed into a shape which was inscribed in a circle 1.4 mm in diameter in the toothbrush of Example 1.

Example 11

A toothbrush was produced following the procedure of Example 1 except that the tufts 6,6 having a triangular cross section are formed into a shape which was inscribed in a circle 4.5 mm in diameter in the toothbrush of Example 1.

Example 12

A toothbrush was produced following the procedure of Example 1 except changing the center-to-center distance between the tufts 6, 6 having a triangular cross section to 11.0 mm in the toothbrush of Example 1.

Comparative Example 1

A toothbrush was produced following the procedure of Example 1 except changing the center-to-center distance between the tufts 6, 6 having a triangular cross section to 3.5 mm in the toothbrush of Example 1.

Comparative Example 2

A toothbrush was produced following the procedure of Example 4 except changing the center-to-center distance between the tufts having a quadrilateral cross section to 3.5 mm in the toothbrush of Example 4.

Comparative Example 3

A toothbrush was produced following the procedure of Example 5 except changing the center-to-center distance between the tufts having a circular cross section to 2.5 mm in the toothbrush of Example 5.

The toothbrush of each Example and each Comparative Example produced as described above were analyzed for cleaning properties (plaque clearance properties) by the following method. The results are shown in Table 2, and the criteria for evaluating cleaning properties are shown in Table 3.

(Evaluation Method of Cleaning Properties)

An artificial plaque was attached to the upper jaw first-molar part of a jaw model. Then, the jaw model was placed in a brushing simulation device, one end of a bristle filling part of the toothbrush was brought into contact with the upper jaw first molar, and then the toothbrush was placed in such a manner that the bristle filling part covered the first molar. Brushing was performed for 3 seconds under a load of 300 g by adjusting the stroke in the horizontal direction to 20 mm. The area of the artificial plaque was measured and calculated by an image analyzer for each part. Then, a ratio of the area where the artificial plaque was removed to the area where the artificial plaque was attached was defined as a plaque removal rate. The cleaning properties of each part were evaluated based on the obtained plaque removal rate.

TABLE 2 Evaluation of cleaning properties Diameter of Total evaluation Cleaning properties of each part Arrangement Center-to-center inscribed circle of cleaning Marginal or of tufts distance(mm) (mm) Bristle properties Total gum line Interproximal part Example 1 Δ--Δ 7.0 2.7 Usual bristle 4 ◯ ◯ ⊚ Example 2 Δ———Δ 9.4 2.7 Usual bristle 4 ◯ ◯ ⊚ Example 3 ∇--∇ 7.0 2.7 Usual bristle 3 ◯ ◯ ◯ Example 4 □--□ 7.0 — Usual bristle 3 ◯ ◯ ◯ Example 5 ◯--◯ 7.0 — Usual bristle 3 ◯ ◯ ◯ Example 6 Δ--Δ 7.0 2.0 Usual bristle 3 ◯ ◯ ◯ Example 7 Δ--Δ 7.0 4.0 Usual bristle 3 ◯ ◯ ◯ Example 8 Δ□Δ 7.0 2.7 Usual bristle 5 ⊚ ⊚ ◯ Example 9 Δ□Δ 7.0 2.7 Special bristle 6 ⊚ ⊚ ⊚ Example 10 Δ--Δ 7.0 1.4 Usual bristle 2.5 ◯ ◯ Δ Example 11 Δ--Δ 7.0 4.5 Usual bristle 2 ◯ Δ Δ Example 12 Δ---Δ 11.0 2.7 Usual bristle 2 ◯ Δ Δ Comparative Δ-Δ 3.5 2.7 Usual bristle X ◯ ◯ X Example 1 Comparative □-□ 3.5 — Usual bristle X ◯ ◯ X Example 2 Comparative ◯-◯ 2.5 — Usual bristle X X X X Example 3

TABLE 3 Criteria for evaluating cleaning properties of each part Total Marginal or gum line Interproximal part {circle around (0)} 90 or more 80 or more 60 or more ◯ 85 or more 70 or more 50 or more Δ 80 or more 60 or more 45 or more X Lower than 80 Lower than 60 Lower than 45 * The numerical values represent a plaque removal rate (%).

It should be noted that the comprehensive evaluation of cleaning properties shown in Table 2 represents the grade of functions of toothbrush products. In the evaluation of cleaning properties in each part, “{circle around (0)}” was scored as 2 points, “◯” was scored as 1 point, and “Δ” was scored as 0.5 point. The respective evaluation scores were summed. Then, it was determined that a toothbrush product having a higher total evaluation score had a higher cleaning effect. The comprehensive evaluation not satisfying the criteria was graded as “X”. More specifically, in the evaluation of cleaning properties in each part, it was determined that a toothbrush which was graded as “X” in any evaluation was also graded as “X” (rejection) in the comprehensive evaluation for judgment of the function. A toothbrush which was not graded as “X” both in the comprehensive evaluation and the evaluation in each part was accepted.

As is clear from Table 2, the toothbrush of the present invention in which tufts are arranged adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance between the centers of the tufts becomes substantially equal to the length in a width direction of a tooth is excellent in cleaning properties over the teeth. In particular, by arranging tufts having a triangular cross section in such a manner as to be tapered from the outer edge of a head portion toward the central axis of the toothbrush, cleaning properties in the interproximal part are excellent. Moreover, by arranging tufts having a quadrilateral cross section between the above-mentioned tufts having a triangular cross section, cleaning properties in the cervical margin are improved. Furthermore, by the use of a tip branched bristle (special bristle), cleaning properties in the interproximal part and the cervical margin are further improved.

INDUSTRIAL APPLICABILITY

According to the toothbrush of the present invention, the tufts in the bristle filling part is well fitted to the interproximal part, especially the interproximal-papilla part, and thus the cleaning properties and the plaque removal efficacy in the parts are excellent. For example, when tooth brushing is performed by a scrub method in which tooth brushing is effected by bringing the bristle tip of the toothbrush into contact with the teeth in a perpendicular manner (in the central axis direction of the toothbrush), and then minutely moving the toothbrush forward and backward or the Bass method in which tooth brushing is effected by bringing the bristle tip of the toothbrush into contact with the boundary between the teeth and the gingival slantingly, and then minutely moving the toothbrush forward and backward, the tufts are easily fitted to the interproximal part. Thus, the toothbrush of the present invention can be suitably used for tooth brushing by the scrub method or the Bass method. 

1: A toothbrush, comprising a tufted portion in which a plurality of tufts formed of bristles made of synthetic resin are fixed to a head portion of a toothbrush body made of synthetic resin, some of the plurality of tufts having substantially the same horizontal cross sectional shape, and being arranged adjacent to each other in a central axis direction of the toothbrush in such a manner that a distance between centers of the tufts becomes substantially equal to a length in a width direction of a tooth. 2: The toothbrush according to claim 1, wherein the distance between centers of the tufts having the same cross sectional shape and arranged adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance between the centers of the tufts becomes equal to the length in the width direction of a tooth is 5 to 12 mm. 3: The toothbrush according to claim 1, wherein the tufts having the same cross sectional shape and arranged adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance between the centers of the tufts becomes equal to the length in the width direction of a tooth are arranged at a side edge of the head portion. 4: The toothbrush according to claim 1, wherein a horizontal cross sectional shape of the tufts having the same cross sectional shape and arranged adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance between the centers of the tufts becomes equal to the length in a width direction of a tooth is a substantially triangular cross sectional shape; and the tuft having a substantially triangular cross sectional shape is fixed to a head portion while a tapered part of a substantially triangular cross sectional shape directing in the same direction. 5: The toothbrush according to claim 4, wherein the tuft having a substantially triangular cross sectional shape has a substantially triangular cross sectional shape which is tapered from the outer edge of the head portion toward the central axis of the toothbrush. 6: The toothbrush according to claim 4, wherein the tuft having a triangular cross sectional shape has a horizontal cross sectional shape which is inscribed in a circle having a diameter of 1.4 to 4.5 mm. 7: The toothbrush according to claim 4, wherein tufts having an elongated cross sectional shape extending in the central axis direction of the toothbrush are arranged between a plurality of tufts having a triangular cross sectional shape and arranged in the central axis direction of the toothbrush. 8: The toothbrush according to claim 7, wherein the tuft having an elongated cross sectional shape is arranged outward in a width direction of the head portion relative to the tuft having a triangular cross sectional shape. 9: The toothbrush according to claim 7, wherein a horizontal cross sectional shape of the tuft having an elongated cross sectional shape is substantially quadrilateral. 10: The toothbrush according to claim 1, wherein bristles tips forming the tufts having the same cross sectional shape and arranged adjacent to each other in the central axis direction of the toothbrush in such a manner that the distance between the centers of the tufts becomes substantially equal to the length in a width direction of a tooth are tapered. 11: The toothbrush according to claim 10, wherein the bristle whose tip is tapered is branched at a tip thereof. 12: The toothbrush according to claim 10, wherein a tuft formed of bristles whose tips are rounded in a usual manner is fixed to a position closer to the central axis of the toothbrush relative to a position of the tufts formed of the bristles each having a tapered tip. 13: The toothbrush according to claim 1, wherein a brush tip surface formed of tip surfaces of tufts is uneven. 14: The toothbrush according to claim 13, wherein a central portion of a tip surface of each tuft formed of tip surfaces of bristles is formed into a convex shape. 15: The toothbrush according to claim 10, wherein a length of the bristle having a tapered tip is substantially equal to or longer than a length of the bristle whose tip is rounded in a usual manner. 16: The toothbrush according to claim 1, wherein the tuft is thermally bonded to the head portion. 17: The toothbrush according to claim 16, wherein the number of the bristles of the tuft is substantially an integral multiple of the number of bristles which are picked out by a device for picking out bristles in the same amount when the tuft is thermally bonded to the head portion. 18: The toothbrush according to claim 16, wherein a horizontal cross sectional area of the bristles of the tuft is substantially an integral multiple of a horizontal cross sectional area of bristles in an opening from which bristles are picked out by a device for picking out bristles in the same amount when the tuft is thermally bonded to the head portion. 